The present invention relates to a system for manufacturing chopped strands of glass filaments, and more particularly to a method and an apparatus for introducing a strand of glass filaments onto a feed roller of the system.
Japanese Patent Publication No. 50-27089 discloses a method of manufacturing chopped strands of glass filaments directly from strands of glass filaments which are formed such that a multiplicity of glass filaments extruded through orifices at the bottom of a spinning furnace and applied with a sizing agent are corrected to form the strand. More particularly, the strand of glass filaments is taken up by a single feed roller to contact the circumferential surface thereof through a predetermined angle so that glass filaments of the strand are drawn and attenuated by frictional force due to the contact with the surface of the feed roller. A cutter roller is disposed to contact under pressure the circumferential surface of the feed roller, thereby cutting the strand into chopped strands of a predetermined length. The position of the feed roller where the cutter roller contact the circumferential surface of the feed roller is selected so that the frictional force imparted to the strand is greater than a drawing force by which normal attenuation of glass filaments of the strand is attained.
In order to increase the productivity of the manufacture method, there has been proposed that a plurality of spinning furnaces are disposed in juxtaposed relationship with each other and a plurality of strands formed of glass filaments extruded from the respective spinning furnaces are taken up by a single feed roller in parallel with each other and cut into chopped strands. However, such a "multi-furnace and multi-strand" system has been unsatisfactory in operation in many respects. For instance, when one of the strands is broken, the introduction of the broken strand onto the feed roller not only is very cumbersome but also produces some serious problems.
In general, in the operation of the above mentioned system, the strands are formed of glass filaments extruded approximately at a rate of 30 to 50 meters per minute from the perspective spinning furnaces. The strands are taken up for attenuation by the feed roller which rotates at high circumferential speed, approximately 1500 to 3000 meters per minute. Therefore, it is very dangerous to introduce the broken strand onto the feed roller while the system continues operation. As a consequence, upon introducing the borken strand onto the feed roller, the feed roller must be slowed down or completely stopped for ensuring safty situation to operators. In other words, the introduction of the broken strand must be made at the sacrifice of the productivity of the system. Furthermore, since glass is a thermo-softening material, streams of molten glass extruded through orifices in the bottom of the spinning furnace must be always drawn under a proper tension to allow the attenuation into filaments. If the drawing force is removed, the molten glass streams would conglomerate into a relatively large bead or beads on the undersurface of the spinning furnace. It is extremely cubersome to remove such a glass bead. Therefore, more than two operators are required for ensuring proper extrusion of glass filaments from all of the spinning furnaces, which is one of the factors which hinder the optimization of the operation of the system.
Furthermore, in the beginning of the operation of the conventional system, the strands consisting of glass filaments in non-attenuation are first brought into engagement with the circumferential surface of an end portion of the feed roller, and thereafter the speed of the feed roller is gradually increased to a normal attenuation speed. After having been completely attenuated, the strands are moved to a cutting portion of the feed roller and the cutting operation is started. However, during the cutting operation, the non-attenuated filaments taken up at the end portion of the feed roller tend to loosen gradually so that pieces like fluffs may fly out and drop and are mixed with the normal chopped strands, which leads to lowering the quality of a product. Additionally, the non-attenuated filaments are relatively thick and have high rigidity so that it is difficult to have them completely engage or wound on the circumferential surface of the feed roller. Therefore, a portion of the strand length tends to move away from and wave about the feed roller with relatively large radii. This is very dangerous to the operators. One method of avoiding the problem is to rapidly increase the speed of the feed roller to a normal attenuation speed after the strands have been taken up by the feed roller so that the length portion of the strand arrested by the roller may be shortened as much as possible. In this case, however, since the strand is rapidly subjected to tension, they are likely to be broken again. Also, rapid wear of the feed roller may occur. An alternate method is to directly introduce the non-attenuated filament strand onto the cutting portion of the feed roller while the speed of the feed roller is gradually increased to a normal attenuation speed. In this method, only chopped strands of glass filaments in normal attenuation are selected and carried out as a commercial product. With this case, however, since the non-attenuated filaments are relatively thick and have high rigidity as above mentioned, the cutter roller must be pressed against the feed roller under a considerably high pressure. As a result, the cutter blades are likely to be filled with chopped strands therebetween so that effective cutting operation is affected adversely. Also, rapid wear of both the feed and cutter rollers would occur. Furthermore, since the thick and rigid non-attenuated filaments are wound on the circumferential surface of the feed roller covered with an elastic material, the surface tends to be formed with corresponding grooves which result in incomplete cutting of the strand. Additionally, when unskilled persons attend to such operation, they tend to erroneously introduce onto the feed roller the strand of glass filaments which has not been cooled sufficiently. As a result, the feed roller is burnt and the cutter blades are broken. Particularly, when the cutter blades are broken, the pieces will fly out at high velocity, injuring nearby operators.